Building: For the FIPS module checksum, keep track of configuration,h

Building: For the FIPS module checksum, keep track of configuration,h

The FIPS module checksum needs to know that configuration.h is
generated from configuration.h.in, so that information is conserved.
To make this possible, it's now possible to have attributes with the
GENERATE keyword, and the attribute "skip" is added to make a keyword
a no-op, which makes it informative only.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Todd Short <todd.short@me.com>
(Merged from https://github.com/openssl/openssl/pull/16378)